Spatiotemporal interactions in detection of texture orientation modulations.

Previous studies have revealed spatial and temporal characteristics of texture orientation modulation detection. This study examined spatiotemporal interactions. We measured threshold amplitudes for detecting orientation modulations in various waveforms. The orientation modulations were presented in a dynamic texture display in which the spatial arrangement and mean orientation of elements were randomly updated at a given frame duration (17-900 ms). The results of three experiments all indicated significant spatiotemporal interactions. As the frame duration was decreased, the detection sensitivity declined more steeply for the sinusoidal orientation modulations than for the square and missing-fundamental waveforms (Expt 1), declined more steeply for low spatial-frequency sinusoidal modulations than for high frequency ones (Expt 2), and declined more steeply for sparse textures than for dense textures (Expt 3). These results indicate that the visual system loses its sensitivity more profoundly for long-range orientation modulations than for short-range modulations as the rate of orientation change increases, suggesting that the mechanism for detecting orientation modulation reduces its effective spatial range for rapid input changes.